Live center



Sept. 27, 1938. v. F. LIPIPARD LIVE CENTER Filed larch 13, 1937 mg 65 6' "WWW/:52

v H .17 20 t 9 23 5 8 1o 24 awe whoa, I 26 164M]! LIPPARD Patented Sept. 27, 1938 UNITED STATES PATENT OFFICE 12 Claims.

The present invention relates toa live center for tail stocks in metal working machines.

The invention is applicable to any type of machine in which a pieceof work is'supported between centers, and is rotated by. driving means, during which rotation 'a metal working operation is performed upon the'piece of work;

The invention comprises essentially a live center assembly, in which the center that'supports the work is adjustable transversely of the assembly in order 'to support the work eccentrica'lly upon its axis of rotation.

One object of theinventi'on is to provide a live center assembly having means whereby the center may be adjusted to rotateeccentrically of the assembly.

Another object 'is'to provide micrometer adjustment means, whereby the degree of "eccentricity may be controlled.

Still another object is to provide means "for insuring the turning of the center with the work in order to cause the r'otarymot'i'on of the -work to be eccentric..

Still another objectfis to provide "supporting means for the end of the work engaged by the center in a yielding manner to permit eccentric rotation.

The field to which theinvention is particularly directed, and in connection with which it was developed, is that of grinding pistons.

In modern internal combustion engines, and especially automobile engines, 'it'is customary to use pistons that are not truly cylindrical. The pistons that are used are what are termed in the industry as cam-ground pistons, which means that they are slightly oval in form, particularly adjacent their tops, this being to 'all'o'w for unequal expansion due to the'pin supporting structure carried within the pistons.

In manufacturing pistons it is customary to form the pistons in the form of a true cylinder, and then by a grinding operation, bring the pistons to the requisite slightly oval "form. Heretofore this grinding operation has been'performed by highly complicated and expensive grinding machines. By means of the present invention this grinding operation may 'be performed by any ordinary grinding machine. In addition to the above described use, the invention is applicable to turning, or any other field of'm'etal working where it is desired to "form "an eccentric object.

In the accompanying drawing:

Figure 1 is an elevation showing "schemati- *cally a piston supported between an "adapter and Figure '2.

Figure 5 is a sectional view of the center assembly. V i

Figure '6 is a sectional view on the line 66 of Figure 5.

Describing the drawing more particularly, and referring first to Figures 5 and 6, the live center assembly includes a s'upporting element 1 having--15 the form of a, standard taper, but which may be of any desired configuration to fit the tail stock of a machine. At its forward end the supporting member 1 may carry a flange 8 extending annularly, and forming the rear walk 20 of "a bearing enclosure 9. Extending forwardly centrally of the flange 8 is a stud III that supports one element ll of a ball race I2, the element 11 being advantageously mounted on the stud I0 b-y'a press fit.

Revolubly carried by the stud Ill and bearing member H is a head l3 comprising an annular cup-like member 14 having a frontwall I5 and circular side wall 16. Theside wall l6 "carries internally a ball race member I! advan-s30 tageously press fitted therein and cooperating with the member H and balls I 8 to revolvably support the head l3 upon the stud ID. The side wall l6 has edges formed to cooperate with the edges of the wall 8 to form a grease seal to ex- 535 "elude dirt and to maintain a supply of lubricant within the enclosure '9. A grease port l9 may be provided.

-It will be seen from the "structure so far disclosed that the head I3 is concentrically re- 40 'volv'a'bleupon the stud I0. In order'to provide for adjustable eccentric rotation, the following center structure is provided.

'The front wall l5 "of the head I3 is provided with a transverse dovetailed mortise 20, the '45 said mortise passing through the center of rotation of "the head. Advantageously the mortise may be formed in a projecting rib-like extension 2! formed integrally with the wall l5,

"and having at each side a shoulder 22.

'Slidably mounted within the mortise 20 and shaped to closely engage the sides of the mortise is a carriage member 2 3 preferably substantially equal in length "to the diameter of the front Wall 15. Themember'2'3 carries at its central portion 55 a cone-shaped center 24 that projects forwardly of the front face 25 of the rib 2|, and that is designed to engage and support the center of the piston or other work to be operated upon. An adlusting screw 26 controls the position of the carriage 23 and therefore of the center 24. The screw 26 is threaded into a bore 21 in the wall I 5 of the head, the bore being positioned closely adjacent the inner surface of the mortise 20. Preferably the threads of the bore 21 andof the screw 26 are of a micrometer type, so that longitudinal movement of the screw will bear a definite relation to its amount of rotation. The screw 26 has an enlarged head 21a that overlies and engages the end of the carriage 23. It will be apparent that upon rotation of the screw in a direction to cause the head to travel toward the center of the assembly the enlarged head 21a. bearing upon the end of the carriage 23, will cause the carriage to move in a direction of motion of the screw. Preferably the screw is provided with a pointer, as at 28 in Figure 2, and the wall of the head is provided with a scale 29, so that a determined adjustment may be easily made. Upon the opposite side of the head is mounted a, backing screw 30 threaded into the wall] l5, and having an enlargedhead 3| that contacts the opposite end of the carriage 23. By means ,of this screw, the carriage may be secured in adjusted position and by tightening the screw, the carriage will be tightened against the head 21a of the screw 26, insuring that the scale reading is accurate. A scale 29a may also be provided in the front face of the assembly.

From the foregoing description, it will be apparent that rotation of the head l3 upon the stud ID will cause the center 24 to revolve in a planetary manner around the center of rotation of the assembly, assuming that the carriage has been moved to place the center in a position removed from the center of rotation of the assembly. It

will also be apparent that the circular rotation of the center will cause a piece of work held between the center and a driving center of a machine, to rotate in an eccentric manner.

In order to insure that the desired eccentric rotation will occur, instead of concentric rotation between centers that are not in line, it is necessary to insure that the head I 3 rotates upon the stud l0. Means are provided for insuring rotation of the head l3 by the rotating work. This means is provided in the form of spring fingers 32 mounted upon the front face of the wall I5 at either side of the rib member 2|, and abutting the shoulders 22 thereof. The spring fingers include end portions 33 that lie closely adjacent the surface, and which are held by screws 34 having heads that overlie these end portions. The fingers proper are bent outwardly and extend angularly forwardly from the portions 33 and in a direction, opposite to that in which the head rotates, and terminate in sharp cornered edges 35.- Thesharp corners of the edges 35 engage the surface of the work, as shown in Figures 1 and 2, with sufficient security to insure that the head l3 rotates upon the stud I0. Inasmuch as the rotation of the work is eccentric, the distance between the face of the work, as the .top surface 36 of the piston 37, shown in Figures 1 and 2, and the front surface of the head, constantly varies. The resilient nature of the spring fingers 32 permits this variation.

In Figures 1 and 2 is illustrated, somewhat schematically, the method of use of the center assembly. A piston 31 is shown mounted between the center 24 and the head stock 38 of a grinding machine, the head stock being provided with an adapter 39 equipped with a driver 40 in accordance with standard practice. The driver extends forwardly from the adapter and engages 5 one of the pin bosses 4| of the piston to rotate the piston.

Assuming that it is desired to eccentrically grind the top portion of the piston, as shown in Figure Z, the screw 26 isturned to give the proper 10 degree of eccentricity of rotation to the piston, as

indicated by the scale 29. With the grinding .instrumentality of the grinder set at the proper distance, the machine is started, and as the piston rotates eccentrically, the grinder will operate 5 upon a portion of its surface at each revolution.

"'When the grinding operation has been completed uponone side of the piston, the piston is reversed in'its position with relation to the center so that the opposite side may be ground. The reversing 20 operation may be accomplished by holding the head I3 against'rotation, and by hand turning the head, stock 38in adirection reverse to its normal. direction of rotation, or it may be accomplishe d..]oy holding the, piston and turning 25 l the head,,l.3 in a forward direction. In either" method thefsh'arp edges of the fingers will slide easily over.fthe top surface of the piston. The

reverse motion may be imparted to the'head stock from any suitable part of the machine that is go accessible to thehand of the operator.

In order that the grinding may take place at theproperpoint on the surface of the piston, the center of the head of the screw 26 is lined up with the center of'the pin hole 42 of the piston, and.

upon reversal of the piston, as above described,"

the opposite pin holeis lined up with the screw 26. The head of the screw 26 indicates the portion, that during the rotation of the piston, is

farthest from the centerof rotation of the head. Where ,itis desired to grind oif a portion of a ,-piston other than that adjacent the pinhole, the

portion to be operated upon may be easily selected by lining it up withthe screw 26. Referring further to Figures 1 and 2 it is some-. 45 times necessary thata piston be cam-ground only in its uppermost portion, while sometimes it is necessary to, cam-grind the piston throughout its length. Where only the upper portion is intended to be ground, the, procedure as above described,

is correct. Where, however, it is necessary to cam-grind a piston throughout its length it becomes necessaryto rotate the complete piston,

adapter 39 and the inner surface of the piston.

- Where it is desired togrind off the same amount of the piston throughout its length and along one side, the material 42 will be selected of the same width as the amount that the center 24 is moved off center. It will be readily realized that different degrees of taper in the ground area may 5 be provided by relating the thickness of the material 42 to the adjustment off-center of the center 24. 7

By use of this center assembly, any sort of cocentric operation may be performed in a machine 7 ,in which the work is supported between centers.

While it has been described as applied to a machine for grindingpistons, it will be readily apparent that it may be-applied to other metal working machines in which the work is revolved.

The assembly provides for controlling the eccentricity given to the rotation of the work with the utmost precision. The assembly is simple and relatively inexpensive to construct, and by its use, an ordinary rotary metal working machine may be used for operations that heretofore required the use of complicated and highly specialized machines.

It is an essential feature of the invention that the adjustment of the center with respect to the center of rotation be located forwardly of the bearing assembly that permits turning of the head with respect to the stationary portion of the assembly, because an adjustment located rearwardly of the bearing assembly would result merely in two out-of-line centers, by means of which a tapered piece of work could be produced, but which would not cause eccentric rotation of the work. Similarly a dead center adjustable to a position out of line with the driving center will result in a tapered piece of work, rather than an eccentric one because the work rotates upon a dead center and does not result in eccentric rotation of the work.

From the foregoing it is thought that the construction, operation and many advantages of the herein described invention will be apparent to those skilled in the art without further description, and it will be understood that various changes in the size, shape, proportion and minor details of construction may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention.

What I claim, is:

1. In a live center assembly for machines, a stationary stud for mounting in the tail stock of a machine, a head rotatably mounted on the stud, and a center movably mounted on the front face of the head for adjustment transversely of the head.

2. In a live center assembly for machines, the

said assembly including a stationary stud and a head rotatably mounted on the stud, a center mounted on the front face of the head for movement transversely of the head, and work-engaging means carried by the head for engaging work supported by the center for driving the head from the work.

3. In a live center assembly for machines, the said assembly including a stationary stud and a head rotatably mounted thereon, and having a front face, the combination with a center mounted on the front face of the head and adjustable transversely of the face, of spring means carried by the face and located out of the line of adjustment of the center, the said spring means extending from the face of the head to a point where they are engageable with work engaged with the center.

4. In a live center assembly for machines, the said assembly including a stationary stud and a head rotatably mounted thereon and having a front face, the combination with a center mounted on the front face of the head and adjustable transversely of the face, of spring fingers secured to the face at either side of the center, and extending angularly outward. from the face of the head and in a direction opposite to the direction of rotation of the machine.

5. A live center assembly for machines comprising a stationary stud, a head rotatably mounted on the stud and having a dovetailed mortise extending transversely across its front end and passing through the center of rotation, a carriage member slidably engaged in the mortise, means for securing the carriage against movement in the mortise, a forwardly extending center mounted upon the carriage, and spring fingers mounted at either side of the mortise, the said fingers each extending angularly forward of the face in a direction opposite the direction of motion of the machine and forwardly of the front face of the head to a point to be engaged by work in the machine.

6. In a grinding machine, the combination with a driving center and a tail stock substantially in line with the driving center, of a live center having a stationary stud engaged in the tail stock and substantially in line with the driving center, a head rotatably mounted on the stud, and a center movably mounted on the rotatable head and for transverse adjustment thereon.

7. In a machine for eccentrically grinding pistons, a revoluble support for one end of a piston, a second revoluble support for the other end of the piston, and means carriedby the second revoluble support for holding the end of the piston h in eccentric relation to the axis of rotation of the said second revoluble support.

8. In a machine for eccentrically grinding pistons, including a head stock and a tail stock, the combination with a driving support for one end of a piston, of a live tail-center comprising a stationary stud mounted in the tail stock, a head rotatably mounted on the stud and transversely adjustable means carried by the revoluble head i for supporting the other end of the piston.

9. In a live center comprising a stud for stationary mounting in a machine, a head revolubly mounted upon the stud and having a front surface, and a center movably mounted on the front face of the head, and at one side of the center line of the stud for eccentric rotation about the axis of the stud.

10. In a live center comprising a stud for stationary mounting in a machine, a head revolubly mounted upon the stud, and having a mortise extending transversely of its front face, a center slidably mounted in the mortise, and screw threaded means carried by the revoluble head for adjusting the position of the center in the mortise, the said screw threaded means being accessible at the side of the head for operation while the center is mounted in a machine.

11. The process of eccentrically grinding pistons that comprises supporting a piston between centers, rotating one center and the end of the piston supported thereby eccentrically, and during said rotation grinding off a portion of the piston along a line parallel to the center of rotation of the piston.

12. The processof eccentrically grinding pistons that comprises rotating a piston eccentrically between centers, during such rotation grinding off a portion of one side of the piston along a line parallel to its center of rotation, reversing the eccentricity of rotation of the piston between the centers by rotating the piston with respect to the centers, and grinding off a second portion of the piston on the opposite side to that first ground along a line parallel to the center of rotation of the piston and during its rotation.

VAN F. LIPPARD. 

